The effect of dilution, pH and ionic strength of plasma on t-PA precipitation in euglobulin fraction.

In order to evaluate the influence of dilution, pH and ionic strength on the precipitation of t-PA and PAI-1 during euglobulin precipitation, we measured t-PA Ag, PAI-1 Ag and fibrinolytic activity in the euglobulin fraction made of pooled plasma from liver cirrhosis patients, under various conditions by changing pH, ionic strength and degree of dilution. The precipitation of t-PA Ag in the euglobulin fraction was enhanced by decreasing the ionic strength and greatest at pH 6.0. The fibrinolytic activity in the euglobulin fraction showed consistent changes with t-PA Ag under varying pH and ionic strength. The precipitation of t-PA Ag was not influenced by the dilution factor but the larger the dilution factor, the greater the PAI-1 and the smaller the fibrinolytic activity in the euglobulin fraction. PAI Ag in euglobulin fraction showed consistent changes with t-PA Ag in the euglobulin fraction regardless of the changes in ionic strength and pH. The amount of precipitation of t-PA and PAI-1 was increased by the presence of dextran sulfate, under varying pH, ionic strength and dilution conditions. Our results show that the currently used conditions for standard euglobulin precipitation are the most favorable for t-PA precipitation into the euglobulin fraction. The fibrinolytic activity exerted in the euglobulin fraction seems to depend on the amount of t-PA-PAI-1 complex rather than minimized protease inhibitor in the euglobulin fraction.